Direct synthesis of phenol from benzene over hydroxyapatite catalysts

The direct synthesis of phenol from benzene in the gas phase was studied ov er hydroxyapatite catalysts. The reaction was carried out in a fixed-bed re actor at atmospheric pressure and reaction temperature of 450 degrees C in the presence of ammonia. A high selectivity (about 97%) of phenol formation at about 3.5% conversion of benzene was achieved over catalysts containing Ca and Cu ions in the cation part of hydroxyapatite. Besides phenol as the main reaction product. aniline is also formed. The reaction mechanism invo lves formation of N2O from NH3 in the first step of reaction. Benzene is ox idized by active oxygen species which are formed on the catalyst by decompo sition of N2O. (C) 2000 Elsevier science B.V. All rights reserved.